Adjustable-length steering columns are known, in which the casing unit which rotatably mounts a shaft of the steering spindle, which shaft supports the steering wheel, can be adjusted in the longitudinal direction of the steering spindle. Here, in one advantageous embodiment, the steering spindle has two shafts which can be telescoped with respect to one another, the rear shaft (in relation to the driving direction) which adjoins the steering wheel being mounted rotatably with respect to the casing unit via first and second anti-friction bearings and being held non-displaceably in the axial direction. The front shaft which can be telescoped with respect to the rear shaft is mounted rotatably by means of a third bearing which is formed by a plain bearing with respect to a housing part of the steering column, which housing part is non-displaceable in the axial direction of the steering shaft. Here, said plain bearing supports the lower shaft against axial displacement with respect to the housing part which mounts it.
In a steering column of this type, in which the rear shaft is mounted in the casing unit by way of two bearings, the arrangement of a third bearing leads to redundancy which leads to a technically satisfactory result only by way of narrow tolerance requirements. Here, in order for it to be possible to compensate for knocking of the shaft, which knocking is caused by tolerances of the shaft and its mounting via the first and second bearing, the third bearing is conventionally configured as a swinging bearing. The swinging bearing is arranged in a bearing housing which surrounds it, forms the interface between the swinging bearing and that part of the steering column which holds the third bearing, and serves to compensate for tolerances. In order to provide overload protection for the third bearing, a steel disc is arranged on the shaft axially next to the third bearing. High forces which act on the third bearing in the radial direction are produced, for example, during the slipping coupling test for the latching star which is usually positioned directly next to the third bearing. Said latching star serves, together with a latching pin which engages into it, to form a steering wheel lock. If the steering wheel is rotated with a high force in the closed state of the steering wheel lock, the latching star has to be capable of slipping on the shaft.
One disadvantage of the described conventional configuration of the plain bearing is its multiple-piece construction (swinging bearing, bearing housing, steel disc) with the associated costs and the resulting weight of the arrangement.
EP 0 836 980 B1 has disclosed a plain bearing for rotatably mounting a shaft of a steering spindle, which plain bearing comprises a sleeve and a holder. The sleeve has a cylindrical section and, protruding axially from the latter, a plurality of projections which are separated by way of slots and the axial end sections of which form the bearing face on their inner sides. On their outer sides which lie opposite, the projections have latching lugs. The holder is snapped via the latching lugs onto the projections and has a planar section which lies at a right angle with respect to the longitudinal axis and oblique holding tongues which project radially to the outside beyond the planar section of the holder. Said holding tongues block a movement of the bearing with respect to the housing part which receives the bearing in the axial direction.